Manufacture of paraffin waxes



Sept. 25, 1951 H. s. BURK MANUFACTURE 0F PARAFFIN wAxEs Filed March 10, 1948 Nm; ENVA@ Patented Sept. 25, 1951l '-UNlTED STAT lm'lNUFAoTom? or ranArFIN wAxEs Herbert Stanley Burk, Maplewood, La., assignor to Gulf Researchxda Development Company,

Pittsburgh, Pa., a corporation of Delaware Application March lo, 193.18, serial No. 14,042

This invention relates to the manufacture'fof paraffin waxes, and in particular concerns an improved process for recovering crystalline paraflin waxes from slack wax. Y Y A In the processing and refining of petroleum oils, the wax-like components thereof are usually.

separated and recovered by initially distilling the oil to obtain a so-called wax distillate ffraction, and thereafter subjecting `such fraction to refrigeration and lter pressing. The wax product recovered from they filter-press is a soft unctuous material comprising the crystalline paraffin waxes and from 25 to 60v per cent by Vweight of oil. This product, knownV as slack wax, is of little commercial value and must be further processed to remove or substantially reduce its oil content. This is accomplished by subjecting the slack wax to a so-called sweating operation which consists essentially in lgradually raising the temperature of the wax while permitting the oil and lower-melting wax components to drain away from the highermelting waxes. By repeating this operation a Anumber of times with suitable recycling of the low-melting waxes, it is possible to separate the slack wax into an arbitrary number of fractions ranging fromA liquid oil through waxes of low and intermediate melting points to the scale waxes and refined waxes which comprise the higher-melting wax components of the original petroleum oil. Such operation, however, is notably ineflicient in that it is inherently time-consuming and is not well adapted to continuous practice. Even under optimum conditions of operation with extensive recycling g of the intermediate wax fractions, the yield of the more valuable waxes of higher melting point is relatively low. Many attempts, have been made to improve the efiiciency of the sweating operation, but except for certain improvements in the mechanical equipment employed, little progress has been made and the process has remained essentially unchanged over a period of years.

It is accordingly an object of the present invention to provide an improved process for recovering crystalline parain waxes from oillcontaining waxes such as slack wax.

Another object is to provide a slack wax relining process which is less vtime-consuming than the conventional sweating process.

A further object is to provide a continuous process for reflning slack wax. l

A still further object is to provide a process for rening slack wax whereby improved yields 3 claims.' (Cl. 19e- 17)- ofthe higher-melting wax components are ata tained.

Other'objects will be apparent from the fol'- lowing detailed description of they invention, and various advantages not 4speciiically referred to hereinwill become apparent to those skilled lin the art upon Vemployment of the invention in' lcomponent of the slack wax. Such process may vbe operated so as to separate the slack wax into oil and wax fractions similar to those obtained by 'the conventional sweating procedure, but effects such separation with a higher degree of selectivity-and with consequent improvement in 'the yield sf the higher-melting products. Also,

since initially increasing 'the porosity of the wax mass'y enables the use lof mechanical equip- Iment to forcibly expel the oil and liquied low- 'melting waxes from the mass, the process "is much less time-consuming than the conventional sweating operation wherein licjuidy is separated fromsolid wax by force of gravity alone. Furthermore, since such mechanical equipment may be of a type adapted for continuous operation,

th'e process may be carried out in a continuous manner with consequent operational and economical advantages.

Referring now to the single figure of the aclcompanying drawing, which is a diagrammatic representation of a flow sheet illustrating one embodiment of the process of the invention,"it

will'be seen that the process is preferably carried vout infa number of separate stages, the first of whichrconsists in mixing the slack wax with ne- `ly divided inert porous material and thereafter subjecting theresulting mixture to a liquid-expelling operation carried out at the temperature at which it is desired to remove the first oil and/or wax fraction, e. g. at 20-25 C. The

variety of porous materials which may be employed for admixing with the slack wax'is limited only by the requirement that the material be of porous structure and inert toward petroleum oils and waxes, e. g., Wood sawdust, grain hulls and other cellulosic materials, asbestos lloc, diatomaceo'us'earth, etc. Wood sawdust is preferred byv reason of its low cost and availability. `As is porous material may be employed in-.the.initial stage, and the wax-saturated material obtained in the final stage may be put to other uses,- as for example in the manufacture of wax-impregnated sheet products, etc.

The mixing operation may be carried! out .in various ways. Preferably, the slack wax is `warmed to the temperature to be employedin the subsequent liquid-expelling operation, andthe inert-.porous materialf which has likewise'been .warmedto such temperature, is then mixed-into rthe-.wax to obtain a homogeneous composition. Alternatively, the slack wax may be ventirely .meltedandvadmixed with the inert porous material while in the liquid state. Such procedure 'obviates the use'of heavy mixing equipment, but -onrthe-other hand necessitates cooling the mixture-beforefsubjecting it to the liquid-expelling operation.

The amount of' porous material adm-ixed-with :the slack: waxy dependsY upon the nature of -both .the'wax and the porous material. There should -be-suflicient porous material present to permit lthe ready-expulsion ofliquid components from 5the Wax mass, but atthe same time thereshould K.notl beso Ymuch that the handling of an excessive -amount of the -porous material is required. Ordinarily, the optimumamount of inert fporous material will be. between about 5-and about 10 per vcent byfweight of the slack wax,although. with some `types `of' slack-:waxas much as 25 per. cent ot the porous-.material maybe required.

The lliquid-expelling operation to -which the -mixture yofslackwax and inert porous material zis. subjected is: carried out in such manner-that zthe liquid content of the vmixture is forciblyex- .pelled from the mass. The use of centrifuges, Vparticularly those` of the continuoustype, is preferredA for thiswoperationfalthough other types -oi equipment may also be employed. Thetem- -perature at which the initial liquid-expelling operation is effected depends upon the nature of .the slack wax undergoing treatment and-v Aupon the degree of renement to be secured inthe .initial stage. Ordinarily it is desirablev thatthe vinitial stage of the process results in the-separa- ;tion of onlyv the normally-'liquid oil components loffv the slack wax. Accordingly, with. conventional slack waxes; the Ainitial liquid-expelling- `operation is usually carried out at/approximately room temperature, e.-g., at about25 C.,'a1 l though higher temperatures -may be employed `if there 'is no objection 'to-separating low-me1ting fwaxes' along with the normally liquid oil.

The second and subsequent stagesof `the process.- with exception of Vthe-final stage, consist merely1inI additional liquid-expelling operations, :each of which is carried out at a .temperature higherV than that of the preceding stage. :The `.number of such stages, and the -temperature'at A'whicheach is carriedrout will depend uponthe #number of. fractions; of oil and low. .and inter- ,stageof `the process. :and sawdust was then subjected to a first liquid- 4 mediate-melting waxes desired. Ordinarily at least two such intermediate stages are employed so that there is obtained, in addition to the oil fraction separated in the initial stage, a first intermediate fraction essentially comprising lowmelting waxes, i. e., waxes having a melting point below about 45 C., a second intermediate fractionessentially comprising intermediate-melting waxes, i. le., waxes having a melting point between about 45 C. and about 55 C., and a residue 1-comprising a mixture of the high-melting waxes and the. inertporous material.

In such a process,the'intermediate stages are usually carried outat temperatures of about 3545 C. and about 45ZL55A C., respectively. If desired, one or more of the intermediate stages may comprise r`several liquidfexpelling operations carried out at the same temperature. Thus, in the figure, Stage II isshown as consisting of two liquid-expelling operations, both of which are carried out at a temperature vof about 36-44 C., whereas-Stage III consists ofa'single liquid-expelling operation .carriedaout at a temperature of about ll4 .50 C. Similarly, as illustrated by the figure, eachof the liquid-expelling operations may be preceded' by a-mixing operation which serves to insure uniform temperature and homogeneous composition fin. the rwax mass. Such mixing operation, however, is not essential to the successful operation Yof the process, and if desired the Wax mass may be .passed .directly from one liquid-expelling operation to the next.

-The final stage -of the process consists in separating the mixture of inert porous material and high-meltingwax which is obtained as a solid residue from the final liquid-expelling operation. Such separation is conveniently carried out by nheating the mixture to a temperature above the .melting point of the wax and thereafter separating the inert .porous material from the liquid wax .by centrifuging, filter-pressing, settling, or other vconvenient operation. 4Alternatively, if desired,

the .mixture may bedissolved in an organic solvent andthe solidporous material separated. by

simple filtration or other means. The wax may then be recovered from the solution by refrigerationand ilteringfor by distilling off the solvent. UsuallyA the waxfproduct is iinished in the conventional manner -by treatingv it with clay, sulfuric acid, etc., to improve its color.

.Ina typical operation of the process of the invention, 200 lparts by weight of a slack .wax obtained from van East Texas crude and having a melting. point of about 45.6 C.A and a liquid oil .content of `about 25 per cent by weight were warmed to a .temperature of about 21 C. and

then mixedwithi42 yparts by weight of wood sawdust. The latter contained about 4.0 per cent by .weight of parain wax having a melting point of about50 C.,-and was typical of the wax-impregnated sawdust product separated in the nal The mixture of slack wax expelling operation carried out by centrifuging `for 1 minuteat a speed of 3600 R. P. M. while maintaining a temperature. of about 21 C., whereby thereA was removed about 40.5 parts by Weight of oil. Thesolid residue was heated to a temperatureof about 42 C., and after mixing to .insure ay homogeneous composition, was subjected to a second liquid-expelling operation carried out by centrifuging vfor 1 minute at a speed of 3600 R. P. M. while .maintaining a temperature of zabout 42 C. Approximately` 57.5 parts by weight 4,ofliquiiied low-melting waxeswere removedby the second centrifuging operation. The solid residue was then melted and ltered to separate the sawdust from the high-melting wax components, whereby there was obtained 93.6 parts by weight of scale wax having an oil content of 2.2 per cent and a melting point of about 51.6 C.

While the above-described procedure serves to illustrate in a general way the operation of the process of the invention, it is to be understood that many variations in operating procedure are permitted within the scope of the invention. In particular, the number of separate liquid-expelling operations and the temperatures at which they are carried out may be arbitrarily varied depending upon the desired degree of separation of the various components of the crude slack wax. Ordinarily, it will be desirable to employ at least three liquid-expelling operations carried out at successively higher temperatures, but in some instances two or even one of such operations may be sufficient to effect the desired degree of refinement. Similarly, the process may be carried out batch-wise, semi-continuously, or fully continuously employing well-known engineering techniques, and any or all of the intermediate products separated may be recycled back to a prior stage of operation one or more times.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the process herein disclosed provided the step or steps stated by the following claims, or the equivalent of such stated step or steps, be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. The process for the manufacture of parailin wax from a slack wax consisting of crystalline waxes and from about 25 to about 60 per cent by weight of oil, which comprises preparing a mixture consisting of said slack wax and between about 5 and about 25 per cent by Weight of wood sawdust, centrifuging said mixture at a temperature between about C. and about 25 C: to separate therefrom the normally liquid oil content of the slack wax, subjecting the residue to a second centrifuging operation at a temperature between about 35 C. and about 45 C. to separate therefrom low-melting wax components, subjecting the residue from said second centrifuging operation to a third centrifuging operation at a temperature between about 45 C. and about 55 C. to separate therefrom intermediatemelting wax components, and separating the wood sawdust from the wax residue from said third centrifuging operation.

2. The process for the manufacture of paraflin wax from a slack wax consisting of crystalline paraffin waxes and from about 25 to about 60 per cent by weight of oil, which comprises preparing a mixture consisting of said slack wax and an inert porous material, subjecting said mixture to at least one centrifuging operation at a temperature between the melting point of the highest melting component of the slack wax and the solidication point of the lowest melting component of the slack wax to separate from said mixture the normally liquid oil content of the slack wax and the wax liquid at the temperature employed, and thereafter separating the inert porous material from the solid wax residue remaining from said centrifuginf,r operation. 3. The process for the manufacture of paraffin wax from a slack wax consisting of crystalline parain waxes and from about 25 to about 60 per cent by weight of oil, which comprises preparing a mixture consisting of said slack wax and an inert porous material, subjecting said mixture to a centrifuging operation at room temperature to separate therefrom the normally liquid oil content of the slack wax and subjecting the solid wax residue to a plurality of centrifuging operations at temperatures between the melting point of the highest melting component of the slack wax and the solidication point of the lowest melting component of the slack wax, each of said centrifuging operations being carried out on the solid residue remaining from the preceding centrifuging operation and at a temperature higher than that of the preceding centrifuging operation, thereby separating from the solid residue at each of the temperatures employed the Wax liquid at said temperatures, and thereafter separating the inert porous material from the solid wax residue remaining from the nal centrifuging operation.

HERBERT STANLEY BURK.

REFERENCES CITED The following references are of record in the le of this lpatent:

UNITED STATES PATENTS Number Name Date 1,278,023 Rosenbaum Sept. 3, 1918 1,509,325 Weir et al Sept. 23, 1924 1,577,852 Petty Mar. 23, 1926 1,678,298 Patrick et al July 24, 1928 1,714,133 Phillips et al May 21, 1929 1,847,488 Lindgren et al. Mar. 1, 1932 1,939,946 Baylis Dec. 19, 1933 2,145,784 Anderson et al. Jan. 31, 1939 

1. THE PROCESS FOR THE MANUFACTURE OF PARAFFIN WAX FROM A SLACK WAX CONSISTING OF CRYSTALLINE WAXES AND FROM ABOUT 25 TO ABOUT 60 PER CENT BY WEIGHT OF OIL, WHICH COMPRISES PREPARING A MIXTURE CONSISTING OF SAID SLACK WAX AND BETWEEN ABOUT 5 AND ABOUT 25 PER CENT BY WEIGHT OF WOOD SAWDUST, CENTRIFUGING SAID MIXTURE AT A TEMPERATURE BETWEEN ABOUT 20* C. AND ABOUT 25* C. TO SEPARATE THEREFROM THE NORMALLY LIQUID OIL CONTENT OF THE SLACK WAX, SUBJECTING THE RESIDUE TO A SECOND CENTRIFUGING OPERATION AT A TEMPERATURE BETWEEN ABOUT 35* C. AND ABOUT 25* C. TO SEPARATE THEREFROM LOW-MELTING WAX COMPONENTS, SUBJECTING THE RESIDUE FROM SAID SECOND CENTRIFUGING OPERATION TO A THIRD CENTRIFUGING OPERATION AT A TEMPERATURE BETWEEN ABOUT 45* C. AND ABOUT 55* C. TO SEPARATE THEREFROM INTERMEDIATEMELTING WAX COMPONENTS, AND SEPARATING THE WOOD SAWDUST FROM THE WAX RESIDUE FROM SAID THIRD CENTRIFUGING OPERATION. 